Archaeologists are continuing to unravel the complex history of Australia’s Aboriginal people, the world’s oldest civilisation.
A new study shows they have occupied South Australia’s Riverland region for 29,000 years – since before the Last Glacial Maximum – which is 22,000 more than previously thought.
It also offers insights into how the first Australians adapted to periods of dramatic environmental change, given the uniquely fluctuating, unpredictable nature of this section of the River Murray.
As the 2500 kilometre-long river enters South Australia, it starts to flow through a deeper confined valley, explains Flinders University’s Craig Westell, first author of a paper published in the journal Australian Archaeology.
“This setting is a bit of a double-edged sword,” he says; “it contains flood water when it arrives, but when flows are low, saltwater enters the floodplains from saline aquifers around the cliff lines.”
The impact of these changing climates became profoundly clear during Australia’s prolonged drought from late 1996 to 2010, when extensive salinisation had critical ecological ramifications.
Such conditions would have challenged Aboriginal people during periods of climatic stress, including the cold, dry environment of the Last Glacial Maximum.
“When we look at the deeper timeline of floodplain development, it’s clear that there were prolonged periods of severe stress – the Millennium Drought on steroids,” says Westell.
“The dating aims to inform a picture of how people have adapted and innovated in this unique setting.”
The researchers conducted an extensive survey spanning 200 kilometres of the River Murray to find archaeological sites they could map to different periods of physical landscape development, up to the late Holocene.
They applied radiocarbon dating to 31 samples of freshwater mussel shells (primarily Alathyria jacksoni), reflecting meals eaten by Aboriginal people long ago, carefully collected from an area overlooking the Pike River floodplain downstream from Renmark.
A standout feature of the findings, says Westell, includes the rapid appearance of extensive freshwater mussel shells that blanketed the valley cliff lines around 15,000 years ago.
This coincides with profound changes in the river, when it was replaced by a more sinuous, regularly flowing body of water. This would have provided a better environment for freshwater mussels, which the ancient tribes exploited.
“The development of these middens points to the dynamism in Aboriginal societies: here we see a change in hydrology and ecology met with a rapid reconfiguration, or a changing emphasis in economy,” says Westell.
“It speaks to that deep, intimate knowledge of country and an ability to respond quickly to change.”
According to co-author Amy Roberts, the work forms part of a larger five-year collaboration with traditional owners – the River Murray and Mallee Aboriginal Corporation – to explore the region’s past and contemporary connections to country.